This invention relates to restoration of capacity in a network, particularly a telecommunications network.
Cycle-oriented preconfiguration of spare capacity is a recent idea originated at TRLabs for the design and operation of restorable networks. It offers a valuable combination of attributes, mainly: it retains the capacity-efficiency of a mesh-restorable network, but it requires that only two nodes, the end nodes next to the fault, perform cross-connections for restoration. Moreover these nodes learn or can be told in advance what switching actions will be required, in detail, for any prospective failure. They can, thus, perform restoration switching in a manner that is essentially similar in function and speed to bi-directional line switched rings. This is thought to be a valuable combination of the best features from prior ring and mesh restoration principles. The work so far done on this scheme has been reported this June at two conferences and described in a patent application [1. W. D. Grover, D. Stamatelakis, xe2x80x9cCycle-Oriented Distributed Preconfiguration: Ring-like Speed with Mesh-like Capacity for Self-planning Network Restoration,xe2x80x9d Proceedings of IEEE International Conf. On Communications (ICC""98), Atlanta, June 1998, pp 537-543, 2. W. D. Grover, D. Stamatelakis, xe2x80x9cSelf-organizing closed path configuration of restoration capacity in broadband and mesh transport networks,xe2x80x9d Proceedings of IEEExe2x80x94Nortel Can. Conf. Broadband Research (CCBR""98), Ottawa, June 1998, pp. 145-156 and 3. U.S. patent application Ser. No. 08/893,491, which was filed Jul. 11, 1997].
These works describe the use of a nodal switching device at nodes of the networks being configured for restoration. A digital cross-connect switch (DCS) is given as an example. A DCS is a technically sound option for deployment. However, DCS machines continue to be relatively expensive investments for network operators. With the recent advent of dense wave division multiplexing (DWDM) on the fiber optic transmission systems between nodes, it may be more economic in practice to have a specialized nodal switching device to support the p-cycle restoration scheme.
Our main purpose in the present patent proposal is fairly singular and direct; it is to protect the unique and unobvious structure of a fixed-capacity nodal device suited to the p-cycle restoration concept.
In summary, this invention provides a xe2x80x98capacity slicexe2x80x99 nodal switching device (in the ADM-like sense) that is designed for deployment under the p-cycle concept. The device""s key architectural properties are access, east and west interfaces, with one spare and working port, on each of these interface sides, plus at least two straddling side interfaces. The straddling side interfaces each have equal line capacity to those of east and west interfaces, but all are usable for working capacity. In application, the plug cards in the nodal switching device are supplied to provide up to two line signal units on the straddling side of the p-cycle device, per diverse span arriving at the site. Network level deployment and configuration of the devices requires that they be arranged in p-cycles according to the theory in our prior papers (1, 2 and 3).